Saturday, August 14, 2010

Disease suspected in deaths of young cormorants

By Marshall Helmberger

An apparent outbreak of disease has taken a toll on young double-crested cormorants on Lake Vermilion’s Potato Island.

More than 50 of the young birds were found dead this week by a tribal biologist, and others were found with symptoms of neurological damage. The symptoms were similar to Newscastle’s Disease, an avian virus that has taken a toll on cormorant populations elsewhere in Minnesota, but DNR wildlife veterinarian Erika Butler said the actual cause of the bird deaths on Lake Vermilion likely won’t be confirmed for 2-3 weeks.

Newcastle’s Disease mostly affects juvenile birds, and it has proven particularly virulent among cormorant populations. The population of cormorants on Lake Vermilion has increased sharply in recent years, a development that has created concerns for anglers, who view the cormorants as competitors for game fish.

A total of 307 cormorant nests were discovered on Potato Island earlier this year, so the deaths of 50 young birds is unlikely to have much impact on the cormorant population. “It will slow down recruitment this year,” said Butler.

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